The final result of Wellington's mayoral election will not be known until Wednesday, with just 40 votes separating the two front-runners.
Preliminary results show incumbent mayor Kerry Prendergast reclaiming the mayoralty for a fourth term with 24, 468 votes.
However, her nearest rival Celia Wade-Brown has so far registered 24,428 votes, with special ballots still to be counted.
Ms Wade-Brown says the cliff-hanger result is due to the fact many Wellingtonians assumed the incumbent mayor would be the victor. She says her strong show in the polls is due to her campaigning at grassroots level.
Ms Prendergast says it was always going to be difficult for her to win a fourth term, as the electorate may be ready for a change of leadership.
She says if she is declared the winner this will be her final term in office.
Electoral Officer Ross Bly says the Wellington preliminary result is the closest margin between two mayoral candidates that he has seen.
Mr Bly says the final results will be officially notified on Wednesday after 960 special votes are counted.